Can you manufacture water

I am new to chemistry, so this might be a stupid question. Can you manufacture water. If so how? Where could I learn more about it? Would it be hard to make? H20 means 2 hydrogen atoms and one oxygen atom? I would like to learn more? I'm not a very smart doctor!!!

Hydrogen is not neccesarily expensive. You could buy a load of concentrated sulphuric acid, then put it in a U-shaped glass container with an electrode at the top of each end, then apply a DC potential difference accross the two. Hydrogen will be attracted to one and Oxygen to the other (at least, their ions will). Then collect the oxygen and hydrogen, stand well back, ignite the hydrogen in the presence of the oxygen, and there's your water.

Of course all of the equipment, acid and electricity are expensive, but that's besides the point.

Staff: Mentor

Originally posted by lavalamp Hydrogen is not neccesarily expensive. You could buy a load of concentrated sulphuric acid, then put it in a U-shaped glass container with an electrode at the top of each end, then apply a DC potential difference accross the two. Hydrogen will be attracted to one and Oxygen to the other (at least, their ions will). Then collect the oxygen and hydrogen, stand well back, ignite the hydrogen in the presence of the oxygen, and there's your water.

Of course all of the equipment, acid and electricity are expensive, but that's besides the point.

You don't need sulfuric acid. Just use water (with maybe a little salt in it).

I was under the impression that this could not be done with normal water as it dissociated into H+ (well H30+ ions) and OH- ions rather than O2- and H+ ions. I can't really see how a little salt would affect this.
Can you explain to me why it would work then? Plus if you had water to begin with, what would the point be? There's no fun in making water from water.

Staff: Mentor

Originally posted by lavalamp I was under the impression that this could not be done with normal water as it dissociated into H+ (well H30+ ions) and OH- ions rather than O2- and H+ ions. I can't really see how a little salt would affect this.

Sending an electric current through water splits it into hydrogen and oxygen by a process called "electrolysis" and is a common way to manufacture hydrogen. I did it in junior high school. The salt is there to add ions to the water to allow the elecricity to flow. Sulfuric acid is mostly water too. Doing electrolysis on it would yield hydrogen, oxygen and more concentrated sulfuric acid.

Plus if you had water to begin with, what would the point be? There's no fun in making water from water.

Indeed. You suggested it though. In any case, this is the cycle by which a so called "hydrogen economy" would likely work. The catch of course is that you don't gain anything - used this way its just an energy storage medium. There are several threads on it floating around here.

I was also told about electrolysis of water, which is what they said it was at the time, but in a later year when I questioned my teacher about it he said that it couldn't be done with water and there had to be sulphuric acid present (or some other acid).

I assume that this is because there are H+ (H30+) ions floating around in a strong acid solution so most of the work has already been done for you.

Incidentally, water does dissociate a little bit at s.t.p. into it's ions and that is why you can electrocute yourself in a bathtub, because water does condunct electricity. It contains 1.00*10^-7 moles / dm^3 of H+ ions at s.t.p. and that is why it has a pH of 7:

As far as I know, if you remove all of the dissolved mineral salts out of water, (distill/filter it enough) it no longer conducts electricity. It is only conductive because of the salt(s), present in almost all water.

You can get de-ionised water, which means that all other ions have been removed from it, but water dissociates all by itself into H30+ and OH- ions.

Have you heard of the constant Kw? It's the ionic product for pure water at s.t.p. and it takes the value, 1*10^14. It's what you get when you multiply together the concentration of H= ions in the water and the concentration of H30+ ions. ie:

[H30+]*[OH-] = 1*10^-7 * 1*10^-7 = 1*10^-14 mol dm^-3

pH is calculated as follows:

-log10([H30+]), as you should know the pH for pure water at s.t.p. is 7, work out:

-log10(1*10^-7) on your calculator and the answer is 7. If you don't have any H30+ or OH- ions in your solution then that solution doesn't have a pH, but you know that water does have a pH therefore it must have either H30+ of OH- ions in it, as it happens, it has both.

At standard temperature and pressure, yes. The pH of water is 7 (directly in the middle of the scale). If the temperature increases then more water molecules have the energy to dissociate and therefore the concentration of hydrogen ions in the solution will increase, therefore the pH lowers slightly, down to maybe 6.5.
The water is still neutral at this pH because there are an equal number of H+ and OH- ions, it's just that the pH is not 7 anymore. Therefore a pH of 7 does not necessarily mean that a solution is neutral.

If you work out the concentration of hydrogen ions in a solution of pH 7, you will find that it is 1*10^-7 mol dm^-3 (worked out by doing this: 10^-pH).

As far as I know, redshift is a phenomonon that occurs when light coming from other galaxies, that are moving away from us, is stretched because they are moving so fast. I don't really see what this has to do with water.

Perculiar properties of water, well when water freezes, it expands. You would expect that it would decrease in size, because after all in solids the atoms/molecules are closer together. This is not the case for water, I think that liquid water at 0 degrees celcius and ice at -4 degrees celcius have the same density. Below -4 the density of ice is greater than that of water, but between -4 and 0 the density of ice is higher.
The reason why water expands when it freezes is because the molecular crystal lattice that forms, holds the water molecules slightly further apart than they would be in a liquid.
The force responsible for the shape of the lattice is called the van der Waahl's force. It is caused by the repulsion of the electon clouds of the oxygen atoms and the repulsion of the nuclei, but the attraction of the electron clouds of the oxygen atoms to other nuclei in other water molecules. These attractive and repulsive forces create an optimum distance for the molecules to be separated for any fixed temperature, (for higher temperatures, the water molecules have slightly higher energies and so the separation distance for higher energy water molecules tends to be larger).
When water molecules aquire enough energy, the van der Waahl's forces are overcome (they don't go away, they are always there), and so the stucture collapses into something that is more dense where the water molecules are free to slide past each other (liquid water). A good analogy for this is like a building, held up with iron girders running through it. But when the forces provided by these girders are overcome, (usually by dynamite), the building just collapses in on itself forming a smaller, more dense, pile of unordered rubble.

I can't think of any other strange properties of water right now, but when, and if, I do I'll post them.